11/25/2013 12:15 AM PST

"Real Housewives of Atlanta" star Porsha Stewart screwed over her fans and essentially stole several thousand dollars, by showing up hours late for a scheduled event ... so claims the event organizer who was left in tears.

Tanika Olivier tells TMZ ... she hired Stewart to make a 4-hour appearance in Ocoee, Fl. Thursday night. She wasn't just an hour late... or 2 hours ... or 3 hours. She showed up 20 minutes before they folded up tent.

According to Olivier ... Stewart had a bunch of lame excuses -- her flight was delayed ... the driver took her to the wrong hotel ... and they had to make a stop to change into fresh clothes.

Stewart was paid $2K up front -- so claims Olivier -- and she had the nerve to demand the $2K balance. Things got ugly and cops were called.

Police told the girls to settle it on their own and Olivier reluctantly cut Porsha a $2K check... but she tells us she's decided to stop payment ... and she wants the initial 2K back STAT.